This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-206819, field Jul. 7, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a display device which is used, for example, in a remote data control system and to-be-controlled device, in which transmission/reception of power and data communication between the control device and one or more devices to be controlled, are carried out via two power lines (we refer to the display device as a two-wire type display device, hereinafter). The two-wire type display device is used as a stock display device and price display device, which may be attached to, for example, a display shelf on which various types of sales products are displayed.
2. Description of the Related Art
There are conventionally several types of methods each known as a technique for carrying out data and electric transmission/reception communication which is conducted with use of two power lines. One (called the first method here) is that a high-frequency signal is superimposed on a power line in a transmitter side, and transmitted, and only the high-frequency signal is extracted by means of a band-pass filter on a receiver device side. Another one (called the second method here) is that a pulse signal whose phase is modulated is superimposed on two-wire type DC power lines and then transmitted on the transmitter side. Still another one is that a DC power is transformed into a pulse by periodically disconnecting or short-circuiting one of the two DC power lines, and transmitted on the transmitter side and such a pulse signal is separated with use of a pulse transformer on the receptor device.
With the first method, it is not easy to clear the problem of leakage which is innately entailed to a high-frequency signal or its anti-noise property. For this method, a complicated circuit structure or circuit parts having particularly high characteristics must be employed for modulation, and therefore the production cost becomes remarkably high. The second method requires phase separation and therefore it has a certain limitation in the transmission speed. The third method can simplify the circuit structure, but entails the problem of noise in any way. In any of the above-described cases, it is very difficult to use a great number of receiver devices if the transmission efficiency is taken into consideration.
As a solution to the above-described drawback of the conventional techniques, the applicant of the present invention proposed before a two-wire type data and electric transmission/reception communication technique capable of high-speed and high anti-noise mutual communications between transmitter and receiver, as well as using a plurality of receiver devices, without having leakage of a transmitted power (Japanese Patent No. 2787976).
According to this technique, to summarize, a transmitter-side device is structured such as to make power levels on two power lines into equivalent pulse-like power on the basis of pulse group data containing the address and instruction data of a receiver-side device. Further, the receiver-side device is structured such as to rectify the equivalent pulse-like power received from the two power lines and store it, and to make power levels on the two power lines into equivalent pulse-like power on the basis of pulse group data containing the address of the self device and the data addressed to the transmitter-side device. In each side, the power supply is stopped while receiving power.
However, the above-described two-wire type data and electric transmission/reception communication technique still entails a drawback to be solved.
More specifically, in the case where the transmission and reception of power and data communication are conducted through the two-wire type device, there is a possibility of misjudging the polarity of data when pulse group data flow in time-series. The judgment of the polarity of data has an influence on the contents of the pulse group data after they are recognized by the receiver-side device. Therefore, it is extremely importance to accurately judge the polarity, for example, in the case where a power receiver device is remotely controlled by a power transmitter device.
In most of the cases, a receiver device can be set on or removed from the power line while the line is in an active state (that is, it can be replaced while current is being carried through the line). However, in order to accurately judge the polarity of data, it is necessary to turn off the entire system including the transmitter-side device when a receiver device is set on (into a state where current is not carried). Therefore, in the case of such a system that involves a great number of receiver devices, the operation of these devices is greatly influenced.
Data stored in a receiver device is usually utilized independently within the device itself, and therefore it is not possible to write arbitrary data therein from the receiver side or to read such data at an arbitrary time. If such writing or reading of data can be performed flexibly, it is expected to facilitate the remote control of the receiver-side device by the transmitter-side device while the transmitter device monitoring the receiver device.
Since the receiver device uses the stored power as its power source, it is important for it to reduce the power consumption as much as possible. Therefore, there must create here an inventive idea to maintain the best possible performance in function while keeping the structure of the hardware which consumes the power should be limited to the minimum necessary level. Especially when the receiver-side device includes display means, the power consumption by the display device cannot be neglected.
The present invention has been proposed to solve the above-described drawback of the conventional technique, and its main object is to provide a two-wire type remote control system which can accurately judge the polarity of data on a receiver side.
Another object of the present invention is to provide a two-wire type remote control system of a general usage of a wide variety, having so various functions and yet suppressed power consumption.
According to a first aspect of the present invention, there is provided a two-wire type remote control system comprising: a wiring case including two power lines; a control device comprising: a generator for generating pulse group data representing an assigned address of a target device to be controlled and control data addressed to the target device; and a power controller for converting DC power into power in equilibrium pulse waveform according to the generated pulse group data, and supplying the converted power to the two power lines; and at least one device to be controlled which is removably attached to the wiring case such that the control device ant the at least one to-be-controlled device are electrically connected to each other via the two power lines, comprising: a charger for rectifying the converted power received from the two power lines, to be charged therein; a polarity identifying circuit for detecting continuation of a logical level of the pulse group data included in the received power for a certain period of time, and identifying a polarity of the pulse group data; a data processor for determining whether or not the assigned address of the self device is included in the received power according to the identified polarity, extracting control data from the pulse group data when the assigned address of the self device is included in the received power, and executing data processing according to the extracted control data; and a display for displaying a result of the data processing by the data processor.
It may be arranged that the at least one to-be-controlled device further comprises: a data generator for generating another pulse group data representing the assigned address of the self device and response data to the control device; and a power controller for converting the power stored by the charger into power in equilibrium pulse waveform according to the another pulse group data, and supplying the converted power to the two power lines, and the control device further comprises a data processor for, when the power supply to the at least one to-be-controlled device is stopped by the power controller of the control device, receiving the power from the at least one to-be-controlled device via the two power lines, and decoding the another pulse group data included in the received power.
It may be arranged that the at least one to-be-controlled device further comprises a non-volatile memory which is readable by the data processor of the at least one to-be-controlled device, and the data processor of the at least one to-be-controlled device executes the data processing such that data writing or data reading into/from the non-volatile memory is selectively executed according to a request from the control device.
According to a second aspect of the present invention, there is provided a two-wire type display device which is removably attached to a wiring case including two power lines, and electrically connected to a control device via the two power lines in the wiring case, the control device converting, DC power into power in equilibrium pulse waveform according to pulse group data representing an assigned address of a target destination and control data to the target destination, and supplying the converted power to the two power lines, the two-wire type display device comprising: a charger for rectifying the converted power received from the two power lines, to be charged therein; a polarity identifying circuit for detecting continuation of a logical level of the pulse group data included in the received power for a certain period of time, and identifying a polarity of the pulse group data; a data processor for determining whether or not the assigned address of the self device is included in the received power according to the identified polarity, extracting control data from the pulse group data when the assigned address of the self device is included in the received power, and executing data processing according to the extracted control data; a display for visualizing a result of the data processing by the data processor; a receiver for receiving a data input from an external device; a data generator for generating another pulse group data representing the assigned address of the self device and response data to the control device, the response data including the data input received by the receiver; and a power controller for converting the power stored by the charger into power in equilibrium pulse waveform according to the another pulse group data, and supplying the converted power to the two power lines.
It should be noted here that in place of the display, audio means for notifying by sound, such as a buzzer, can be used. In this case, the result of the data processing is represented by the buzzer sound or voice.
It may be arranged that the display is designed to indicate a letter, a symbol, and/or a numeral by way of a combination of a plurality of display segments thereof, and the display device further comprises a display test circuit for carrying out a display test by turning on the segments one by one consecutively.
With such a display test circuit, the power consumption for a segment test can be significantly reduced, and therefore the device can be operated on stored power without a problem of power shortage.
It may be arranged that the display has a switch for revising a content of display, and the switch is designed to change a display function usually assigned to another display function by means of a software operation. With this structure, so various functions can be realized at a less hardware resource.
It may be arranged that the display device further comprises: a switch for outputting a pulse signal representing one of binary values when the switch is pressed down and a pulse signal representing the other of the binary values when a pressed-down state of the switch is released; and a switch data generator for, when an output value from the switch is changed, generating switch data representing such a change, wherein the switch data is reflected in contents of the response data.
With this structure, a pulse signal is output not only when the switch is pressed down, but also the press-down state is released, and therefore switch data can be generated regardless of the pressing time period of the switch.
It may be arranged that the display device further comprises a pair of wiring members which are connected to the two power lines, respectively upon being attached to the wiring case, wherein a contact point of each of the wiring members is brought into elastic contact with respective one of the power lines.
It may be arranged that the display device further comprises an elastic engagement mechanism for engaging itself to the wiring case by applying a force onto the body of the device in a first direction, and removing it from the wiring case by applying a force thereto in a second direction which is different from the first direction.